A Comparison between Mucoderm® and Connective Tissue Graft for Root Coverage

Statement of the Problem: Subepithelial connective tissue graft (SCTG) is the gold stand-ard treatment for root coverage procedure; however, this technique has limitations such as the need for a donor site and the difficulty of the harvesting procedure. The potential bene-fits of Mucoderm®, a collagen matrix derived from porcine dermis, as an alternative treat-ment for root coverage can be investigated. Purpose: This study aimed to evaluate the efficacy of Mucoderm® for root coverage and compare its results with SCTG. Materials and Method: This double-blind split-mouth randomized clinical trial was con-ducted on seven patients with 12 bilateral gingival recessions (24 recession sites). Coronally advanced flap + Mucoderm® was applied on one side and coronally advanced flap + con-nective tissue graft (CTG) was applied on the contralateral side. We measured the periodon-tal pocket depth (PPD), clinical attachment level (CAL), recession depth (RD), keratinized tissue width (KTW) and gingival thickness (GT) with a surgical stent at baseline (preopera-tively) and at 1, 3 and 6 months postoperatively. The Wilcoxon and Friedman tests were used to analyse the data. Results: The mean percentage of root coverage was 26% in the Mucoderm® group and 60% in the SCTG group at 6 months, compared with baseline. The mean percentage of root coverage was significantly different between the two groups (p Value< 0.05). The results indicated that Mucoderm® did not increase the KTW, while CTG significantly increased the KTW (p Value< 0.05 at 1, 3 and 6 months). Conclusion: The results of this study showed that Mucoderm® might not be an appropriate alternative for the CTG in root coverage procedures.


Introduction
Gingival recession refers to apical migration of the gingival margin relative to the cementoenamel junction (CEJ) [1]. Exposure of the root surface may lead to an unaesthetic appearance, root hypersensitivity, and difficult oral hygiene maintenance. No direct relationship has been reported between gingival recession and tooth loss; however, the progression of buccal gingival recession may compromise the longevity of the tooth [2].
Several techniques have been recommended for root coverage such as the pedicle and free autogenous grafts [3]. At present, subepithelial connective tissue graft (SCTG) is considered as the gold standard for the root coverage procedure [4]. Successful results have been reported using SCTG especially for Miller's class I and II recessions [5]. However, it has some restrictions such as the need for a secondary surgical procedure in the palate to harvest the graft and limited amount of tissue to harvest [6]. To overcome these limitations, allografts and xenografts were introduced to the market [7].
Collagen matrix as an alternative for connective tissue graft (CTG) has been proposed for root coverage procedure in different studies. It has been mentioned that the use of a collagen matrix instead of the CTG could reduce the time of surgery and the pain that the patients suffer during and after surgery [1,[3][4]. However, there are contradicting results regarding the root coverage percentage by using collagen matrices in comparison with the CTG. According to similar studies, the root coverage percentage using collagen matrices have been reported to be in the range of 64% to 96% [3][4].
Mucoderm® (Botiss, Germany) is a xenogeneic collagen matrix derived from porcine. Following the purification procedures, a 3D matrix comprising of types I and type III collagen is produced with a structure similar to that of connective tissue [8]. Only a few studies have evaluated the efficiency of Mucoderm® as an alternative to CTG in periodontal plastic surgery [7,9] Therefore, this study aimed to evaluate the efficacy of Muco-derm® for root coverage compared with the CTG.

Patient selection and preparation
This study was a double blind, split-mouth randomized clinical trial, which was conducted in Department of Periodontics, Faculty of Dentistry, Islamic Azad University, Tehran, Iran. Seven patients with 12 bilateral Miller's class I and II gingival recessions (24 recession sites) participated in this study. Five patients had multiple recessions and two had bilateral single recession sites.
The patients willingly signed informed consent forms prior to their participation in the study. This study was approved by the institute review committee for hu- The patients were non-smokers, did not have systemic or periodontal diseases, were not pregnant or lactating, and did not use medications with adverse effects on the gingiva. The recession sites around decayed teeth, crowns, and orthodontic wires were also excluded from the study. Oral hygiene instructions were provided and non-surgical periodontal treatments were performed to decrease the O'Leary's plaque index of patients below 20%. Patients were also instructed to avoid traumatic tooth brushing.
The study parameters including periodontal pocket depth (PPD), clinical attachment level (CAL), keratinized tissue width (KTW), gingival thickness (GT) and recession depth (RD) were measured at baseline (preoperatively) and at 1,3and6 months postoperatively. PPD was measured from the gingival margin to the bottom of the sulcus, and CAL was measured from the CEJ to the bottom of the sulcus at the midbuccal aspect of the tooth [10]. RD was measured from the CEJ to the gingival margin, and KTW was measured from the gingival margin to the mucogingival junction in the midbuccal aspect of the teeth by using a Williams probe [11]. GT was determined as thin or thick biotype using the transgingival probing technique [12].
In order to avoid possible errors in consecutive measurements, one stent was fabricated for each patient, so the angulation and placement of periodontal probe would be more accurate. All parameters were measured by a periodontist (F.S) who was not aware of the test or control sides of the patients.

Surgical techniques
According to a computer-generated randomization list (Microsoft Excel 2010), one side was treated by Muco-derm® and the contralateral side was treated with CTG.
The incision was made using a #15 carbon steel scalpel (Moris, Germany). One sulcular incision and then two horizontal incisions (Figure1) were made from the base of the mesial papilla to the base of the distal papilla. The horizontal incisions did not reach the adjacent tooth (the vertical distance from the tip of the papilla to the horizontal incision was equal to gingival recession + 1mm).
Two divergent vertical incisions were made coronoapically to 3-4mm beyond the mucogingival junction. A full-thickness flap was elevated apical to the recession site, and split-thickness flaps were elevated at the mesial and distal parts of the recession site. Thus, a trapezoidal flap design was prepared. The exposed root surface was debrided and root-planed, and the adjacent papillae were de-epithelialized. The muscle tensions were released and

Post-surgical considerations
Amoxicillin (500mg; Tehranshimi, Iran) was prescribed 3 times a day for 6 days, and ibuprofen (600 mg; Aria, Iran) was prescribed twice a day for 1 week [1]. The sutures were removed after 2 weeks. The patients were instructed to avoid tooth brushing for 4 weeks and 0.2% chlorhexidine mouth rinse (Shahrdaru, Tehran) was prescribed twice daily [16].

Statistical analysis
To calculate the minimum sample size, we conducted a pilot study on four patients, and t-test on the mean root coverage values after 1 month was performed. The results revealed that a minimum of nine samples were required considering α=0.05, β=0.2 and standard deviation of 34%.
The data were analyzed by Freedman (within-group) and Wilcoxon (between-group) tests. SPSS version 25 (SPSS Inc., IL, USA) was used for statistical analysis, and p Value<0.05 was considered statistically significant.    Table 1. These values were calculated at baseline (T0, preoperatively), and at 1 (T1), 3 (T3) and 6 (T6) months, postoperatively. Table 2 shows the differences between the Mucoder-m® and SCTG for PPD, CAL, RD, KTW, and root coverage using the Wilcoxon Signed Rank test. As shown in Table 2, there was no significant difference in any parameter between the Mucoderm® and SCTG groups at baseline (T0; p> 0.05).

Seven
The mean RD in the Mucoderm®+coronally advanced flap group was 3.83±1.11mm at baseline, which ch-  Three patients had thin and four had thick biotype.
The biotype of all recession sites (whether treated by Mucoderm® or CTG) changed to thick biotype after the surgical procedure. In other words, the patients who had thin gingival biotype acquired thick gingival biotype and those with thick gingival biotype remained the same after surgery.

Discussion
This split-mouth study was performed to compare Mu-coderm® with CTG for root coverage procedure. According to the results of this study, Mucoderm® + coronally advanced flap had inferior results to CTG + coronally advanced flap in terms of root coverage percentage and KTW.
In a systematic review, Amine et al. [17] concluded that SCTG was still the gold standard for root coverage surgery, and xenogeneic collagen matrix had inferior results to the CTG. It should be noted that xenogeneic collagen matrices have variable structures and, in some studies, they showed comparable results to CTGs [1,11]. For instance, McGuire et al. [18] reported comparable results for Mucograft® and CTG for root coverage. Thus, xenogeneic collagen matrices may show variable results depending on their process of production and structure.
Cardopoli et al. [1] and Chevalier et al. [11] did not find significant differences between the CTG and xeno-  Mucoderm®, similar to Mucograft®, is a collagen matrix derived from porcine dermis [19]. However, in order to find an explanation for the poor results of Muco-derm® in this study in comparison with Mucograft®, we need to consider their different structures. Muco-graft® has a bilayer structure. The outer layer is condensed and occlusive but the inner layer has a porous structure, which allows the ingrowth of blood clot and the surrounding tissues [19]. Whilst, Mucoderm® has a uniform 3D structure composed of collagen and elastin [19]. Probably, the inner porous layer of Mucograft® improves tissue integration and better root coverage.
Taba et al. [20]  Mucoderm® is a new collagen matrix and only a few clinical studies have evaluated its efficacy [19,25].
Thus, more studies are needed to assess the capability of this collagen matrix in periodontal plastic surgeries.

Conclusion
According to the results of the present study, Muco-derm® might not be a good alternative to CTG to increase the mean percentage of root coverage and KTW; but Mucoderm® can increase the gingival thickness comparable to the CTG.